Epitaxial thin films of (001)-oriented FeTiO(3+delta) were prepared on alpha-Al2O3(001) single crystalline substrates by helicon plasma sputtering technique. The FeTiO(3+delta) films had large oxygen nonstoichiometry, which seriously depended on both substrate temperature and oxygen pressure during the sputtering deposition. The valence states of Fe ions in FeTiO(3+delta) changed monotonically from Fe2+ to Fe3+ with decreasing the substrate temperature from 900 to 400 degrees C or with increasing the oxygen pressure from 0.9 to 1.8x10(-6) Pa. The change of Fe valence states from Fe2+ to Fe3+ induced the magnetic phase transition only for the films prepared at 900 degrees C. The films containing Fe2+ were paramagnetic while those with Fe3+ were antiterromagnetic at room temperature. The oxygen nonstoichiometry of the FeTiO(3+delta) films was probably produced by cation vacancies and disarrangement of Fe3+ and Ti4+ ions, which randomly occupied both interstitial and substitutional sites of the FeTiO3 related structure.